Pre-dispersed carbon black as conductive agent for LiFePO4 cathodes

Abstract

High dispersed carbon black was applied for LiFePO4 cathodes as conductive agent. Nano-conductive carbon agent was pre-dispersed with poly acrylic acid (PAA) as dispersant in organic N-methyl-pyrrolidone (NMP) solvent system. The dispersion property of nano-conductive carbon agent was evaluated using particle size distribution measurements, scanning electron microscopy (SEM) and transmission electron microscope (TEM). LiFePO4 cathode with as-received nano-conductive carbon agent (SP) and LiFePO4 cathode with pre-dispersed nano-conductive carbon agent (SP-PAA) were examined by scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impendence spectroscopy (EIS) and charge/discharge cycling performance. Results show that the dispersion property of carbon black is improved by using PAA as the dispersant. The LiFePO4 cathodes with SP-PAA exhibit improved rate behaviors (4C, 135.1 mAh/g) and cycle performance (95%, 200 cycles) compared to LiFePO4 cathodes with SP (4C, 103.9 mAh/g and 83%, 200 cycles). Because pre-dispersed carbon black (SP-PAA) is dispersed homogeneously in the dried composite electrode to form a more uniform conductive network between the active material particles, electrochemical performances of the LiFePO4 cathodes are improved.